In the prior art some types of telephone service, especially keyset, substitute flashing lights for the more conventional ringing bell. To do this it is necessary to have a circuit which can detect the ringing signal and operate a suitable common audible output and the flashing lights. In the past, resonant electronic circuits have been used to detect the ringing signal which can range from 16 to 60 hertz. However, such resonant circuits are slow to respond if they are made selective enough to reject being triggered by the 10 or 12 hertz pulses that are produced by dialing. To avoid this problem prior art telephone equipment is designed to disable the ringing detector circuits during dialing. My invention provides a solid state ringing detector which overcomes these disadvantages by being at the same time both responsive and highly discriminatory. The circuit described herein can respond to the ringing signal in as little as two cycles but remain unaffected by the dialing signals so that it is no longer necessary to disable the ringing detector during dialing. Also my invention is less costly to build and adjust than a resonant circuit.